1. Field of the Invention
The present invention relates to a mobile telephone, and in particular to a power supply system of a voice-dialing mobile telephone usable both as an installed telephone and as a portable telephone.
2. Description of the Related Art
With the recent world wide popularization of automobiles, mobile telephones have come into wider use, which in turn has caused the creation of many inventions. Most of these inventions have been intended to ensure safe and reliable use for drivers. In U.S. Pat. No. 4,908,846 issued in 1990, a mobile telephone capable of starting up a call-clear process reliably even when a power switch is depressed by mistake in lieu of a call-end key is disclosed. A drawback of such a mobile telephone has been that a specified key mounted in its operation part has to be depressed and accordingly in order to depress the key, the driver's gaze has to turn to the key from the road, which may cause a dangerous accident to take place. In order to avoid this drawback, the method of starting up a dialing circuit in which a start-up signal is generated from an spoken voice of an isolated word registered previously has been developed. While this method is capable of precluding the above problem in safety, another problem has been encountered that, since the voice dialing circuit has to keep waiting for input of the isolated word assigned to the start-up command, the power source wastes power for the waiting. This power waste is problematic particularly when the mobile telephone is used while receiving a power supply from a built-in battery, because the voice-dialing circuit requires high power consumption on account of high-speed computation.
A mobile telephone is typically constructed to be capable of both being carried outdoors as a portable mobile telephone and being mounted inside the car as an installed mobile telephone, and when it is used as a portable mobile telephone, it receives its power supply from a battery pack. Thus, where the mobile telephone is of the voice dialing type, it is essential to avoid power waste while waiting, i.e., the time which is not spent calling.